P0140 code help

[GTPNovak]

I installed SD headers without cat. I put in a modified o2 sensor (new Bosch sensor) to account for no cat. The modification is a 1 mega ohm resistor and 1 micro farad cap added to the sensor to simulate a cat, it worked great on my Ford. The computer on the GTP is telling me no communication, i collected data and the output of the rear o2 stays steady at 0.450V.

Has anyone tried a circuit like this with success without having to pay to tune out the rear sensor.

I plan to put in an unmodified sensor to see if i get a P0420, if i dont then i know something is wrong with the wire harness. I checked all fuses under the hood and they are good.

Any other ideas to try?

 

[GTPNovak]

I think i figured it out. I installed the cap on the wrong side of the resistor. Waiting for the rain to pass to pull the sensor and redo the circuit.

 

[w3tbanana]

Ive never tried making one. But zzp has one, I cant remember if they have a picture or not. Ill ask my bro, but you need something to send fluctuating signals back. The no comunication is a lack of signal change.

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[GTPNovak]

So after further research and learning the differences in how manufactures monitor cat efficiency the electrical circuit i made will not work for 2000 GM vehicles.
The computer is looking for a fluctuating passing examples 4.5 to -4.5 volts passing zero. The circuit i made dropped the voltage but did not allow it to pass zero. This worked on my Contour SVT because it only looks for a voltage delta front to back.

I was able to get the code to stay off by removing the circuit and installing 2 spark plug non foulers moving the sensor out of the main exhaust stream.

 

[blueguy91]

You could do that; or just leave the rear o2 in there and set the rear o2 to no report in the PCM. Most any 00 or 01+ GM seems to behave better that way with the cat diagnostics running in open or closed loop.